Another battery thread...

OK, I know this has been done to death in the past, but...... I've been away on work for 5 weeks, so was expecting the battery to be dead when I got home. However, It's really dead, not even an attempt to crank, I jumped it from the booster and took it for a drive. After 10 miles I stopped the engine ,(mistake) the battery was still completly dead. Will the alternator charge a battery which is completely dead? I've had it on charge all night and it's still only showing 11.4v and 45% charge... The meter says to replace the battery! The battery is a new Porsche purchase, only 8 weeks old. When running the battery voltage showed 13.5volts, with no load and 12v with load. (leakage 0.02amps....it shouldn't have died!) Is my Alternator dead as well? and does anyone know where I can buy a new regulator for it? I also had the coolant changed, just before all the battery issues started? I understand that a pulled fuse required for the coolant change, kills comms between the dash and the alternator disableing the voltage regulation? :nooo:

A battery left discharged for prolonged periods sustain permanant damage. However a new one left for 5 weeks shouldn't do what you have described. Chances are the new battery from Porsche has been on the shelf for a while and they have not been diligent in keeping it charged up monthly until installed. One way to test it is to test the specific gravity of each cell using a hygrometer. You get them in halfords for a couple of quid. A good cell should have a specific gravity above 1.250 at room temperature and all cells should be the same. The ones that are low indicate duff cells. Also your alternator sounds like its on its way out. Mine was the same as yours and it was just enough to keep the battery going duing the spring and summer but I had it refurbished with new bushes and voltage regulator for £200 which was the best money spent.

Thanks, The battery supplied by OPC is supplied dry, they added the wet stuff and charged it for me 2 days before I picked it up. I've had it on a bigger charger overnight, the voltage reads 12.7v now, so fully charged, but my battery test device still only says 55% (condition of capacity) I'll check each cell tonight. I've put the battery out of my old Carrera on and it starts fine. measurments are.. I have a 200mA leak, so that explains the discharge. (in series with the battery, need to trace, already pulled all fuses) 12v with the engine off. (accross battery terminals) 13.5 Volt with the engine running (accross battery terminals) 13.2 Volts with a load, lights, blower etc (accross battery terminals) Increasing enginer speed makes no differance. Can anybody with a 'good car', measure and confirm for me please.

200mA leak is a lot. New cars can have up to 150mA hence everything shuts down after 5 days in the Porsche. I have a digital battery tester and every new battery I've had only read in the region of 55-60% when it is brand new. Don't know why but an engineer will probably be able to explain it.

If it works ok for a few days in different conditions having charged it then its probably ok as above. If you notice any lack of battery power from normal just take it back to the OPC with your receipt and get them to test it and replace it with a new one

Should be 40mA or so, according to this RennTecher:

I am no expert- but when my brothers brand new battery when flat, he was advised to trickle charge back to life? Maybe thats what you need to do? Kam

A CTEK or similar with pulsed charge (restore) regime can work wonders on reviving old batteries. Although as your battery was new that's not really the point. Can't you ask the OPC?

opps

I could, but...... As I'd like to put an OPC warranty on the car when I get back from my next trip, I dont really want them digging around to much and decide that I need to replace the Alternator before they will cover it. Will it be checked on a 111pt? I'd rather have these problems surface after the warranty has been applied :wink: What I really need is someone to put a meter across the battery terminals and let me know what the charging voltage is... As mine is what I consider to be marginal i.e 13.5v, A duff alternator/regulator may also be the cause of the current leak... If I know for sure that it's duff, I'll pull it myself and get it rebuilt, and save OPC adding a £1000 bill to the warranty. As RH says 40mA sound OK, but 200mA is not... Note: If you buy a fitted battery from OPC, they check the alternator etc as well before fitting.